1. Field
The present invention relates to an electrochromic display that displays images by utilizing an electrochromic phenomenon.
2. Description of the Related Art
Electronic paper is getting more and more attention as a new display medium that combines the characteristics as paper, which is no need of information holding energy, can be securely saved, easily read, quickly readable and so on, and the characteristics as an electronic display capable of rewriting information and so on.
Various types are known as a display principle in the electronic paper. For example, it is a microcapsule type electrophoretic display method where capsules enclosing positively and negatively charged black and white particles are moved between electrodes. Further, it is a twist ball method where the direction of spherical particles colored in black and white are controlled. These methods perform display by utilizing a physical phenomenon.
On the other hand, there is known a method that performs display by utilizing a chemical phenomenon. Among others, one utilizing an electrochromic phenomenon is known where voltage is applied between electrodes to cause coloring or deletion by oxidation-reduction reaction. This is described in Japanese Patent Laid-Open No. 10-232413 publication, for example.
In the case of an electrochromic display utilizing the electrochromic phenomenon, it is constituted that electrodes are formed on each of substrates that make a pair, an electrochromic film is formed on the electrodes, and an electrolytic layer is sandwiched between the both substrates. Coloring agent such as white particles is usually contained in the electrolytic layer for improving contrast. However, the coloring agent is contained in the electrolytic layer at a fixed ratio and target contrast cannot be secured when the electrolytic layer is made too thin, and manufacturing of a thin electrochromic display is thus limited to a certain level.